/*
**
** File: fmopl.c - software implementation of FM sound generator
**                                            types OPL and OPL2
**
** Copyright Jarek Burczynski (bujar at mame dot net)
** Copyright Tatsuyuki Satoh , MultiArcadeMachineEmulator development
**
** Version 0.72
**

** Adapted for use in VICE by Marco van den Heuvel <blackystardust68@yahoo.com>


Revision History:

04-08-2003 Jarek Burczynski:
 - removed BFRDY hack. BFRDY is busy flag, and it should be 0 only when the chip
   handles memory read/write or during the adpcm synthesis when the chip
   requests another byte of ADPCM data.

24-07-2003 Jarek Burczynski:
 - added a small hack for Y8950 status BFRDY flag (bit 3 should be set after
   some (unknown) delay). Right now it's always set.

14-06-2003 Jarek Burczynski:
 - implemented all of the status register flags in Y8950 emulation
 - renamed y8950_set_delta_t_memory() parameters from _rom_ to _mem_ since
   they can be either RAM or ROM

08-10-2002 Jarek Burczynski (thanks to Dox for the YM3526 chip)
 - corrected ym3526_read() to always set bit 2 and bit 1
   to HIGH state - identical to ym3812_read (verified on real YM3526)

04-28-2002 Jarek Burczynski:
 - binary exact Envelope Generator (verified on real YM3812);
   compared to YM2151: the EG clock is equal to internal_clock,
   rates are 2 times slower and volume resolution is one bit less
 - modified interface functions (they no longer return pointer -
   that's internal to the emulator now):
    - new wrapper functions for OPLCreate: ym3526_init(), ym3812_init() and y8950_init()
 - corrected 'off by one' error in feedback calculations (when feedback is off)
 - enabled waveform usage (credit goes to Vlad Romascanu and zazzal22)
 - speeded up noise generator calculations (Nicola Salmoria)

03-24-2002 Jarek Burczynski (thanks to Dox for the YM3812 chip)
 Complete rewrite (all verified on real YM3812):
 - corrected sin_tab and tl_tab data
 - corrected operator output calculations
 - corrected waveform_select_enable register;
   simply: ignore all writes to waveform_select register when
   waveform_select_enable == 0 and do not change the waveform previously selected.
 - corrected KSR handling
 - corrected Envelope Generator: attack shape, Sustain mode and
   Percussive/Non-percussive modes handling
 - Envelope Generator rates are two times slower now
 - LFO amplitude (tremolo) and phase modulation (vibrato)
 - rhythm sounds phase generation
 - white noise generator (big thanks to Olivier Galibert for mentioning Berlekamp-Massey algorithm)
 - corrected key on/off handling (the 'key' signal is ORed from three sources: FM, rhythm and CSM)
 - funky details (like ignoring output of operator 1 in BD rhythm sound when connect == 1)

12-28-2001 Acho A. Tang
 - reflected Delta-T EOS status on Y8950 status port.
 - fixed subscription range of attack/decay tables


    To do:
        add delay before key off in CSM mode (see CSMKeyControll)
        verify volume of the FM part on the Y8950
*/

#include "vice.h"

#include <math.h>
#include <stdio.h>
#include <string.h>

#include "fmopl.h"
#include "lib.h"
#include "snapshot.h"

#ifndef M_PI
#define M_PI 3.14159265358979323846
#endif

#define FINAL_SH (0)
#define MAXOUT   (+32767)
#define MINOUT   (-32768)

#define FREQ_SH  16  /* 16.16 fixed point (frequency calculations) */
#define EG_SH    16  /* 16.16 fixed point (EG timing)              */
#define LFO_SH   24  /*  8.24 fixed point (LFO calculations)       */
#define TIMER_SH 16  /* 16.16 fixed point (timers calculations)    */

#define FREQ_MASK       ((1 << FREQ_SH) - 1)

/* envelope output entries */
#define ENV_BITS 10
#define ENV_LEN  (1 << ENV_BITS)
#define ENV_STEP (128.0 / ENV_LEN)

#define MAX_ATT_INDEX ((1 << (ENV_BITS - 1)) - 1) /*511*/
#define MIN_ATT_INDEX (0)

/* sinwave entries */
#define SIN_BITS 10
#define SIN_LEN  (1 << SIN_BITS)
#define SIN_MASK (SIN_LEN - 1)

#define TL_RES_LEN (256)        /* 8 bits addressing (real chip) */

/* register number to channel number , slot offset */
#define SLOT1 0
#define SLOT2 1

/* Envelope Generator phases */

#define EG_ATT 4
#define EG_DEC 3
#define EG_SUS 2
#define EG_REL 1
#define EG_OFF 0

#define OPL_TYPE_WAVESEL  0x01  /* waveform select     */
#define OPL_TYPE_ADPCM    0x02  /* DELTA-T ADPCM unit  */
#define OPL_TYPE_KEYBOARD 0x04  /* keyboard interface  */
#define OPL_TYPE_IO       0x08  /* I/O port            */

/* ---------- Generic interface section ---------- */
#define OPL_TYPE_YM3526 (0)
#define OPL_TYPE_YM3812 (OPL_TYPE_WAVESEL)

/* mapping of register number (offset) to slot number used by the emulator */
static const int slot_array[32] = {
    0, 2, 4, 1, 3, 5, -1, -1,
    6, 8, 10, 7, 9, 11, -1, -1,
    12, 14, 16, 13, 15, 17, -1, -1,
    -1, -1, -1, -1, -1, -1, -1, -1
};

/* key scale level */
/* table is 3dB/octave , DV converts this into 6dB/octave */
/* 0.1875 is bit 0 weight of the envelope counter (volume) expressed in the 'decibel' scale */
#define DV (0.1875 / 2.0)

static const double ksl_tab[8 * 16] = {
    /* OCT 0 */
    0.000 / DV, 0.000 / DV, 0.000 / DV, 0.000 / DV,
    0.000 / DV, 0.000 / DV, 0.000 / DV, 0.000 / DV,
    0.000 / DV, 0.000 / DV, 0.000 / DV, 0.000 / DV,
    0.000 / DV, 0.000 / DV, 0.000 / DV, 0.000 / DV,

    /* OCT 1 */
    0.000 / DV, 0.000 / DV, 0.000 / DV, 0.000 / DV,
    0.000 / DV, 0.000 / DV, 0.000 / DV, 0.000 / DV,
    0.000 / DV, 0.750 / DV, 1.125 / DV, 1.500 / DV,
    1.875 / DV, 2.250 / DV, 2.625 / DV, 3.000 / DV,

    /* OCT 2 */
    0.000 / DV, 0.000 / DV, 0.000 / DV, 0.000 / DV,
    0.000 / DV, 1.125 / DV, 1.875 / DV, 2.625 / DV,
    3.000 / DV, 3.750 / DV, 4.125 / DV, 4.500 / DV,
    4.875 / DV, 5.250 / DV, 5.625 / DV, 6.000 / DV,

    /* OCT 3 */
    0.000 / DV, 0.000 / DV, 0.000 / DV, 1.875 / DV,
    3.000 / DV, 4.125 / DV, 4.875 / DV, 5.625 / DV,
    6.000 / DV, 6.750 / DV, 7.125 / DV, 7.500 / DV,
    7.875 / DV, 8.250 / DV, 8.625 / DV, 9.000 / DV,

    /* OCT 4 */
     0.000 / DV,  0.000 / DV,  3.000 / DV,  4.875 / DV,
     6.000 / DV,  7.125 / DV,  7.875 / DV,  8.625 / DV,
     9.000 / DV,  9.750 / DV, 10.125 / DV, 10.500 / DV,
    10.875 / DV, 11.250 / DV, 11.625 / DV, 12.000 / DV,

    /* OCT 5 */
     0.000 / DV,  3.000 / DV,  6.000 / DV,  7.875 / DV,
     9.000 / DV, 10.125 / DV, 10.875 / DV, 11.625 / DV,
    12.000 / DV, 12.750 / DV, 13.125 / DV, 13.500 / DV,
    13.875 / DV, 14.250 / DV, 14.625 / DV, 15.000 / DV,

    /* OCT 6 */
     0.000 / DV,  6.000 / DV,  9.000 / DV, 10.875 / DV,
    12.000 / DV, 13.125 / DV, 13.875 / DV, 14.625 / DV,
    15.000 / DV, 15.750 / DV, 16.125 / DV, 16.500 / DV,
    16.875 / DV, 17.250 / DV, 17.625 / DV, 18.000 / DV,

    /* OCT 7 */
     0.000 / DV,  9.000 / DV, 12.000 / DV, 13.875 / DV,
    15.000 / DV, 16.125 / DV, 16.875 / DV, 17.625 / DV,
    18.000 / DV, 18.750 / DV, 19.125 / DV, 19.500 / DV,
    19.875 / DV, 20.250 / DV, 20.625 / DV, 21.000 / DV
};
#undef DV

/* sustain level table (3dB per step) */
/* 0 - 15: 0, 3, 6, 9,12,15,18,21,24,27,30,33,36,39,42,93 (dB)*/
#define SC(db) (UINT32)(db * (2.0 / ENV_STEP))

static const UINT32 sl_tab[16] = {
    SC(0), SC(1), SC(2), SC(3), SC(4), SC(5), SC(6), SC(7),
    SC(8), SC(9), SC(10), SC(11), SC(12), SC(13), SC(14), SC(31)
};
#undef SC

#define RATE_STEPS (8)

static const unsigned char eg_inc[15 * RATE_STEPS] = {
/* cycle: 0 1  2 3  4 5  6 7 */

/* 0 */ 0, 1, 0, 1, 0, 1, 0, 1, /* rates 00..12 0 (increment by 0 or 1) */
/* 1 */ 0, 1, 0, 1, 1, 1, 0, 1, /* rates 00..12 1 */
/* 2 */ 0, 1, 1, 1, 0, 1, 1, 1, /* rates 00..12 2 */
/* 3 */ 0, 1, 1, 1, 1, 1, 1, 1, /* rates 00..12 3 */

/* 4 */ 1, 1, 1, 1, 1, 1, 1, 1, /* rate 13 0 (increment by 1) */
/* 5 */ 1, 1, 1, 2, 1, 1, 1, 2, /* rate 13 1 */
/* 6 */ 1, 2, 1, 2, 1, 2, 1, 2, /* rate 13 2 */
/* 7 */ 1, 2, 2, 2, 1, 2, 2, 2, /* rate 13 3 */

/* 8 */ 2, 2, 2, 2, 2, 2, 2, 2, /* rate 14 0 (increment by 2) */
/* 9 */ 2, 2, 2, 4, 2, 2, 2, 4, /* rate 14 1 */
/* 10 */ 2, 4, 2, 4, 2, 4, 2, 4, /* rate 14 2 */
/* 11 */ 2, 4, 4, 4, 2, 4, 4, 4, /* rate 14 3 */

/* 12 */ 4, 4, 4, 4, 4, 4, 4, 4, /* rates 15 0, 15 1, 15 2, 15 3 (increment by 4) */
/* 13 */ 8, 8, 8, 8, 8, 8, 8, 8, /* rates 15 2, 15 3 for attack */
/* 14 */ 0, 0, 0, 0, 0, 0, 0, 0, /* infinity rates for attack and decay(s) */
};

#define O(a) (a * RATE_STEPS)

/*note that there is no O(13) in this table - it's directly in the code */
static const unsigned char eg_rate_select[16 + 64 + 16] = {     /* Envelope Generator rates (16 + 64 rates + 16 RKS) */
/* 16 infinite time rates */
    O(14), O(14), O(14), O(14), O(14), O(14), O(14), O(14),
    O(14), O(14), O(14), O(14), O(14), O(14), O(14), O(14),

    /* rates 00-12 */
    O(0), O(1), O(2), O(3),
    O(0), O(1), O(2), O(3),
    O(0), O(1), O(2), O(3),
    O(0), O(1), O(2), O(3),
    O(0), O(1), O(2), O(3),
    O(0), O(1), O(2), O(3),
    O(0), O(1), O(2), O(3),
    O(0), O(1), O(2), O(3),
    O(0), O(1), O(2), O(3),
    O(0), O(1), O(2), O(3),
    O(0), O(1), O(2), O(3),
    O(0), O(1), O(2), O(3),
    O(0), O(1), O(2), O(3),

    /* rate 13 */
    O(4), O(5), O(6), O(7),

    /* rate 14 */
    O(8), O(9), O(10), O(11),

    /* rate 15 */
    O(12), O(12), O(12), O(12),

    /* 16 dummy rates (same as 15 3) */
    O(12), O(12), O(12), O(12), O(12), O(12), O(12), O(12),
    O(12), O(12), O(12), O(12), O(12), O(12), O(12), O(12),
};
#undef O

/*rate  0,    1,    2,    3,   4,   5,   6,  7,  8,  9,  10, 11, 12, 13, 14, 15 */
/*shift 12,   11,   10,   9,   8,   7,   6,  5,  4,  3,  2,  1,  0,  0,  0,  0  */
/*mask  4095, 2047, 1023, 511, 255, 127, 63, 31, 15, 7,  3,  1,  0,  0,  0,  0  */

#define O(a) (a * 1)

static const unsigned char eg_rate_shift[16 + 64 + 16] = {      /* Envelope Generator counter shifts (16 + 64 rates + 16 RKS) */
    /* 16 infinite time rates */
    O(0), O(0), O(0), O(0), O(0), O(0), O(0), O(0),
    O(0), O(0), O(0), O(0), O(0), O(0), O(0), O(0),

    /* rates 00-12 */
    O(12), O(12), O(12), O(12),
    O(11), O(11), O(11), O(11),
    O(10), O(10), O(10), O(10),
    O(9), O(9), O(9), O(9),
    O(8), O(8), O(8), O(8),
    O(7), O(7), O(7), O(7),
    O(6), O(6), O(6), O(6),
    O(5), O(5), O(5), O(5),
    O(4), O(4), O(4), O(4),
    O(3), O(3), O(3), O(3),
    O(2), O(2), O(2), O(2),
    O(1), O(1), O(1), O(1),
    O(0), O(0), O(0), O(0),

    /* rate 13 */
    O(0), O(0), O(0), O(0),

    /* rate 14 */
    O(0), O(0), O(0), O(0),

    /* rate 15 */
    O(0), O(0), O(0), O(0),

    /* 16 dummy rates (same as 15 3) */
    O(0), O(0), O(0), O(0), O(0), O(0), O(0), O(0),
    O(0), O(0), O(0), O(0), O(0), O(0), O(0), O(0),
};
#undef O

/* multiple table */
#define ML 2

static const double mul_tab[16] = {
/* 1/2, 1, 2, 3, 4, 5, 6, 7, 8, 9,10,10,12,12,15,15 */
    0.50 * ML, 1.00 * ML, 2.00 * ML, 3.00 * ML, 4.00 * ML, 5.00 * ML, 6.00 * ML, 7.00 * ML,
    8.00 * ML, 9.00 * ML, 10.00 * ML, 10.00 * ML, 12.00 * ML, 12.00 * ML, 15.00 * ML, 15.00 * ML
};
#undef ML

/*  TL_TAB_LEN is calculated as:
 *   12 - sinus amplitude bits     (Y axis)
 *   2  - sinus sign bit           (Y axis)
 *   TL_RES_LEN - sinus resolution (X axis)
 */
#define TL_TAB_LEN (12 * 2 * TL_RES_LEN)
static signed int tl_tab[TL_TAB_LEN];

#define ENV_QUIET       (TL_TAB_LEN >> 4)

/* sin waveform table in 'decibel' scale */
/* four waveforms on OPL2 type chips */
static unsigned int sin_tab[SIN_LEN * 4];

/* LFO Amplitude Modulation table (verified on real YM3812)
   27 output levels (triangle waveform); 1 level takes one of: 192, 256 or 448 samples

   Length: 210 elements.

    Each of the elements has to be repeated
    exactly 64 times (on 64 consecutive samples).
    The whole table takes: 64 * 210 = 13440 samples.

    When AM = 1 data is used directly
    When AM = 0 data is divided by 4 before being used (loosing precision is important)
*/

#define LFO_AM_TAB_ELEMENTS 210

static const UINT8 lfo_am_table[LFO_AM_TAB_ELEMENTS] = {
    0, 0, 0, 0, 0, 0, 0,
    1, 1, 1, 1,
    2, 2, 2, 2,
    3, 3, 3, 3,
    4, 4, 4, 4,
    5, 5, 5, 5,
    6, 6, 6, 6,
    7, 7, 7, 7,
    8, 8, 8, 8,
    9, 9, 9, 9,
    10, 10, 10, 10,
    11, 11, 11, 11,
    12, 12, 12, 12,
    13, 13, 13, 13,
    14, 14, 14, 14,
    15, 15, 15, 15,
    16, 16, 16, 16,
    17, 17, 17, 17,
    18, 18, 18, 18,
    19, 19, 19, 19,
    20, 20, 20, 20,
    21, 21, 21, 21,
    22, 22, 22, 22,
    23, 23, 23, 23,
    24, 24, 24, 24,
    25, 25, 25, 25,
    26, 26, 26,
    25, 25, 25, 25,
    24, 24, 24, 24,
    23, 23, 23, 23,
    22, 22, 22, 22,
    21, 21, 21, 21,
    20, 20, 20, 20,
    19, 19, 19, 19,
    18, 18, 18, 18,
    17, 17, 17, 17,
    16, 16, 16, 16,
    15, 15, 15, 15,
    14, 14, 14, 14,
    13, 13, 13, 13,
    12, 12, 12, 12,
    11, 11, 11, 11,
    10, 10, 10, 10,
    9, 9, 9, 9,
    8, 8, 8, 8,
    7, 7, 7, 7,
    6, 6, 6, 6,
    5, 5, 5, 5,
    4, 4, 4, 4,
    3, 3, 3, 3,
    2, 2, 2, 2,
    1, 1, 1, 1
};

/* LFO Phase Modulation table (verified on real YM3812) */
static const INT8 lfo_pm_table[8 * 8 * 2] = {
    /* FNUM2/FNUM = 00 0xxxxxxx (0x0000) */
    0, 0, 0, 0, 0, 0, 0, 0,     /*LFO PM depth = 0*/
    0, 0, 0, 0, 0, 0, 0, 0,     /*LFO PM depth = 1*/

    /* FNUM2/FNUM = 00 1xxxxxxx (0x0080) */
    0, 0, 0, 0, 0, 0, 0, 0,     /*LFO PM depth = 0*/
    1, 0, 0, 0, -1, 0, 0, 0,    /*LFO PM depth = 1*/

    /* FNUM2/FNUM = 01 0xxxxxxx (0x0100) */
    1, 0, 0, 0, -1, 0, 0, 0,    /*LFO PM depth = 0*/
    2, 1, 0, -1, -2, -1, 0, 1,  /*LFO PM depth = 1*/

    /* FNUM2/FNUM = 01 1xxxxxxx (0x0180) */
    1, 0, 0, 0, -1, 0, 0, 0,    /*LFO PM depth = 0*/
    3, 1, 0, -1, -3, -1, 0, 1,  /*LFO PM depth = 1*/

    /* FNUM2/FNUM = 10 0xxxxxxx (0x0200) */
    2, 1, 0, -1, -2, -1, 0, 1,  /*LFO PM depth = 0*/
    4, 2, 0, -2, -4, -2, 0, 2,  /*LFO PM depth = 1*/

    /* FNUM2/FNUM = 10 1xxxxxxx (0x0280) */
    2, 1, 0, -1, -2, -1, 0, 1,  /*LFO PM depth = 0*/
    5, 2, 0, -2, -5, -2, 0, 2,  /*LFO PM depth = 1*/

    /* FNUM2/FNUM = 11 0xxxxxxx (0x0300) */
    3, 1, 0, -1, -3, -1, 0, 1,  /*LFO PM depth = 0*/
    6, 3, 0, -3, -6, -3, 0, 3,  /*LFO PM depth = 1*/

    /* FNUM2/FNUM = 11 1xxxxxxx (0x0380) */
    3, 1, 0, -1, -3, -1, 0, 1,  /*LFO PM depth = 0*/
    7, 3, 0, -3, -7, -3, 0, 3   /*LFO PM depth = 1*/
};

/* lock level of common table */
static int num_lock = 0;

static void *cur_chip = NULL;   /* current chip pointer */
static OPL_SLOT *SLOT7_1, *SLOT7_2, *SLOT8_1, *SLOT8_2;

static signed int phase_modulation;     /* phase modulation input (SLOT 2) */
static signed int output[1];

static UINT32 LFO_AM;
static INT32 LFO_PM;

inline static int limit(int val, int max, int min)
{
    if (val > max) {
        val = max;
    } else if (val < min) {
        val = min;
    }

    return val;
}

/* status set and IRQ handling */
inline static void OPL_STATUS_SET(FM_OPL *OPL, int flag)
{
    /* set status flag */
    OPL->status |= flag;
    if (!(OPL->status & 0x80)) {
        if (OPL->status & OPL->statusmask) {    /* IRQ on */
            OPL->status |= 0x80;
        }
    }
}

/* status reset and IRQ handling */
inline static void OPL_STATUS_RESET(FM_OPL *OPL, int flag)
{
    /* reset status flag */
    OPL->status &= ~flag;
    if ((OPL->status & 0x80)) {
        if (!(OPL->status & OPL->statusmask)) {
            OPL->status &= 0x7f;
        }
    }
}

/* IRQ mask set */
inline static void OPL_STATUSMASK_SET(FM_OPL *OPL, int flag)
{
    OPL->statusmask = flag;

    /* IRQ handling check */
    OPL_STATUS_SET(OPL, 0);
    OPL_STATUS_RESET(OPL, 0);
}

/* advance LFO to next sample */
inline static void advance_lfo(FM_OPL *OPL)
{
    UINT8 tmp;

    /* LFO */
    OPL->lfo_am_cnt += OPL->lfo_am_inc;
    if (OPL->lfo_am_cnt >= ((UINT32)LFO_AM_TAB_ELEMENTS << LFO_SH)) {     /* lfo_am_table is 210 elements long */
        OPL->lfo_am_cnt -= ((UINT32)LFO_AM_TAB_ELEMENTS << LFO_SH);
    }

    tmp = lfo_am_table[OPL->lfo_am_cnt >> LFO_SH];

    if (OPL->lfo_am_depth) {
        LFO_AM = tmp;
    } else {
        LFO_AM = tmp >> 2;
    }

    OPL->lfo_pm_cnt += OPL->lfo_pm_inc;
    LFO_PM = ((OPL->lfo_pm_cnt >> LFO_SH) & 7) | OPL->lfo_pm_depth_range;
}

/* advance to next sample */
inline static void advance(FM_OPL *OPL)
{
    OPL_CH *CH;
    OPL_SLOT *op;
    int i;

    OPL->eg_timer += OPL->eg_timer_add;

    while (OPL->eg_timer >= OPL->eg_timer_overflow) {
        OPL->eg_timer -= OPL->eg_timer_overflow;

        OPL->eg_cnt++;

        for (i = 0; i < 9 * 2; i++) {
            CH = &OPL->P_CH[i / 2];
            op = &CH->SLOT[i & 1];

            /* Envelope Generator */
            switch (op->state) {
                case EG_ATT:            /* attack phase */
                    if (!(OPL->eg_cnt & ((1 << op->eg_sh_ar) - 1))) {
                        op->volume += (~op->volume * (eg_inc[op->eg_sel_ar + ((OPL->eg_cnt >> op->eg_sh_ar) & 7)])) >> 3;

                        if (op->volume <= MIN_ATT_INDEX) {
                            op->volume = MIN_ATT_INDEX;
                            op->state = EG_DEC;
                        }
                    }
                    break;
                case EG_DEC:    /* decay phase */
                    if (!(OPL->eg_cnt & ((1 << op->eg_sh_dr) - 1))) {
                        op->volume += eg_inc[op->eg_sel_dr + ((OPL->eg_cnt >> op->eg_sh_dr) & 7)];

                        if ((UINT32)(op->volume) >= op->sl) {
                            op->state = EG_SUS;
                        }
                    }
                    break;
                case EG_SUS:    /* sustain phase */

                    /* this is important behaviour:
                       one can change percusive/non-percussive modes on the fly and
                       the chip will remain in sustain phase - verified on real YM3812 */

                    if (op->eg_type) {          /* non-percussive mode */
                        /* do nothing */
                    } else {                            /* percussive mode */
                        /* during sustain phase chip adds Release Rate (in percussive mode) */
                        if (!(OPL->eg_cnt & ((1 << op->eg_sh_rr) - 1))) {
                            op->volume += eg_inc[op->eg_sel_rr + ((OPL->eg_cnt >> op->eg_sh_rr) & 7)];

                            if (op->volume >= MAX_ATT_INDEX) {
                                op->volume = MAX_ATT_INDEX;
                            }
                        }
                        /* else do nothing in sustain phase */
                    }
                    break;
                case EG_REL:    /* release phase */
                    if (!(OPL->eg_cnt & ((1 << op->eg_sh_rr) - 1))) {
                        op->volume += eg_inc[op->eg_sel_rr + ((OPL->eg_cnt >> op->eg_sh_rr) & 7)];

                        if (op->volume >= MAX_ATT_INDEX) {
                            op->volume = MAX_ATT_INDEX;
                            op->state = EG_OFF;
                        }
                    }
                    break;
                default:
                    break;
            }
        }
    }

    for (i = 0; i < 9 * 2; i++) {
        CH = &OPL->P_CH[i / 2];
        op = &CH->SLOT[i & 1];

        /* Phase Generator */
        if (op->vib) {
            UINT8 block;
            unsigned int block_fnum = CH->block_fnum;
            unsigned int fnum_lfo = (block_fnum & 0x0380) >> 7;
            signed int lfo_fn_table_index_offset = lfo_pm_table[LFO_PM + 16 * fnum_lfo];

            if (lfo_fn_table_index_offset) {    /* LFO phase modulation active */
                block_fnum += lfo_fn_table_index_offset;
                block = (block_fnum & 0x1c00) >> 10;
                op->Cnt += (OPL->fn_tab[block_fnum & 0x03ff] >> (7 - block)) * op->mul;
            } else {    /* LFO phase modulation  = zero */
                op->Cnt += op->Incr;
            }
        } else {        /* LFO phase modulation disabled for this operator */
            op->Cnt += op->Incr;
        }
    }

    /*  The Noise Generator of the YM3812 is 23-bit shift register.
     *   Period is equal to 2^23-2 samples.
     *   Register works at sampling frequency of the chip, so output
     *   can change on every sample.
     *
     *   Output of the register and input to the bit 22 is:
     *   bit0 XOR bit14 XOR bit15 XOR bit22
     *
     *   Simply use bit 22 as the noise output.
     */

    OPL->noise_p += OPL->noise_f;
    i = OPL->noise_p >> FREQ_SH;                /* number of events (shifts of the shift register) */
    OPL->noise_p &= FREQ_MASK;
    while (i) {
        /*
           Instead of doing all the logic operations above, we
           use a trick here (and use bit 0 as the noise output).
           The difference is only that the noise bit changes one
           step ahead. This doesn't matter since we don't know
           what is real state of the noise_rng after the reset.
         */

        if (OPL->noise_rng & 1) {
            OPL->noise_rng ^= 0x800302;
        }
        OPL->noise_rng >>= 1;

        i--;
    }
}

inline static signed int op_calc(UINT32 phase, unsigned int env, signed int pm, unsigned int wave_tab)
{
    UINT32 p;

    p = (env << 4) + sin_tab[wave_tab + ((((signed int)((phase & ~FREQ_MASK) + (pm << 16))) >> FREQ_SH ) & SIN_MASK)];

    if (p >= TL_TAB_LEN) {
        return 0;
    }
    return tl_tab[p];
}

inline static signed int op_calc1(UINT32 phase, unsigned int env, signed int pm, unsigned int wave_tab)
{
    UINT32 p;

    p = (env << 4) + sin_tab[wave_tab + ((((signed int)((phase & ~FREQ_MASK) + pm)) >> FREQ_SH ) & SIN_MASK)];

    if (p >= TL_TAB_LEN) {
        return 0;
    }
    return tl_tab[p];
}

#define volume_calc(OP) ((OP)->TLL + ((UINT32)(OP)->volume) + (LFO_AM & (OP)->AMmask))

/* calculate output */
inline static void OPL_CALC_CH(OPL_CH *CH)
{
    OPL_SLOT *SLOT;
    unsigned int env;
    signed int out;

    phase_modulation = 0;

    /* SLOT 1 */
    SLOT = &CH->SLOT[SLOT1];
    env = volume_calc(SLOT);
    out = SLOT->op1_out[0] + SLOT->op1_out[1];
    SLOT->op1_out[0] = SLOT->op1_out[1];
    *SLOT->connect1 += SLOT->op1_out[0];
    SLOT->op1_out[1] = 0;
    if (env < ENV_QUIET) {
        if (!SLOT->FB) {
            out = 0;
        }
        SLOT->op1_out[1] = op_calc1(SLOT->Cnt, env, (out << SLOT->FB), SLOT->wavetable);
    }

    /* SLOT 2 */
    SLOT++;
    env = volume_calc(SLOT);
    if (env < ENV_QUIET) {
        output[0] += op_calc(SLOT->Cnt, env, phase_modulation, SLOT->wavetable);
    }
}

/*
    operators used in the rhythm sounds generation process:

    Envelope Generator:

channel  operator  register number   Bass  High  Snare Tom  Top
/ slot   number    TL ARDR SLRR Wave Drum  Hat   Drum  Tom  Cymbal
 6 / 0   12        50  70   90   f0  +
 6 / 1   15        53  73   93   f3  +
 7 / 0   13        51  71   91   f1        +
 7 / 1   16        54  74   94   f4              +
 8 / 0   14        52  72   92   f2                    +
 8 / 1   17        55  75   95   f5                          +

    Phase Generator:

channel  operator  register number   Bass  High  Snare Tom  Top
/ slot   number    MULTIPLE          Drum  Hat   Drum  Tom  Cymbal
 6 / 0   12        30                +
 6 / 1   15        33                +
 7 / 0   13        31                      +     +           +
 7 / 1   16        34                -----  n o t  u s e d -----
 8 / 0   14        32                                  +
 8 / 1   17        35                      +                 +

channel  operator  register number   Bass  High  Snare Tom  Top
number   number    BLK/FNUM2 FNUM    Drum  Hat   Drum  Tom  Cymbal
   6     12,15     B6        A6      +

   7     13,16     B7        A7            +     +           +

   8     14,17     B8        A8            +           +     +

*/

/* calculate rhythm */

inline static void OPL_CALC_RH(OPL_CH *CH, unsigned int noise)
{
    OPL_SLOT *SLOT;
    signed int out;
    unsigned int env;


    /* Bass Drum (verified on real YM3812):
       - depends on the channel 6 'connect' register:
           when connect = 0 it works the same as in normal (non-rhythm) mode (op1->op2->out)
           when connect = 1 _only_ operator 2 is present on output (op2->out), operator 1 is ignored
       - output sample always is multiplied by 2
     */

    phase_modulation = 0;

    /* SLOT 1 */
    SLOT = &CH[6].SLOT[SLOT1];
    env = volume_calc(SLOT);

    out = SLOT->op1_out[0] + SLOT->op1_out[1];
    SLOT->op1_out[0] = SLOT->op1_out[1];

    if (!SLOT->CON) {
        phase_modulation = SLOT->op1_out[0];
        /* else ignore output of operator 1 */
    }

    SLOT->op1_out[1] = 0;
    if (env < ENV_QUIET) {
        if (!SLOT->FB) {
            out = 0;
        }
        SLOT->op1_out[1] = op_calc1(SLOT->Cnt, env, (out << SLOT->FB), SLOT->wavetable);
    }

    /* SLOT 2 */
    SLOT++;
    env = volume_calc(SLOT);
    if (env < ENV_QUIET) {
        output[0] += op_calc(SLOT->Cnt, env, phase_modulation, SLOT->wavetable) * 2;
    }

    /* Phase generation is based on: */
    /* HH  (13) channel 7->slot 1 combined with channel 8->slot 2 (same combination as TOP CYMBAL but different output phases) */
    /* SD  (16) channel 7->slot 1 */
    /* TOM (14) channel 8->slot 1 */
    /* TOP (17) channel 7->slot 1 combined with channel 8->slot 2 (same combination as HIGH HAT but different output phases) */

    /* Envelope generation based on: */
    /* HH  channel 7->slot1 */
    /* SD  channel 7->slot2 */
    /* TOM channel 8->slot1 */
    /* TOP channel 8->slot2 */


    /* The following formulas can be well optimized.
       I leave them in direct form for now (in case I've missed something).
     */

    /* High Hat (verified on real YM3812) */
    env = volume_calc(SLOT7_1);
    if (env < ENV_QUIET) {
        /* high hat phase generation:
           phase = d0 or 234 (based on frequency only)
           phase = 34 or 2d0 (based on noise)
         */

        /* base frequency derived from operator 1 in channel 7 */
        unsigned char bit7 = ((SLOT7_1->Cnt >> FREQ_SH) >> 7) & 1;
        unsigned char bit3 = ((SLOT7_1->Cnt >> FREQ_SH) >> 3) & 1;
        unsigned char bit2 = ((SLOT7_1->Cnt >> FREQ_SH) >> 2) & 1;

        unsigned char res1 = (bit2 ^ bit7) | bit3;

        /* when res1 = 0 phase = 0x000 | 0xd0; */
        /* when res1 = 1 phase = 0x200 | (0xd0>>2); */
        UINT32 phase = res1 ? (0x200 | (0xd0 >> 2)) : 0xd0;

        /* enable gate based on frequency of operator 2 in channel 8 */
        unsigned char bit5e = ((SLOT8_2->Cnt >> FREQ_SH) >> 5) & 1;
        unsigned char bit3e = ((SLOT8_2->Cnt >> FREQ_SH) >> 3) & 1;

        unsigned char res2 = (bit3e ^ bit5e);

        /* when res2 = 0 pass the phase from calculation above (res1); */
        /* when res2 = 1 phase = 0x200 | (0xd0>>2); */
        if (res2) {
            phase = (0x200 | (0xd0 >> 2));
        }

        /* when phase & 0x200 is set and noise=1 then phase = 0x200|0xd0 */
        /* when phase & 0x200 is set and noise=0 then phase = 0x200|(0xd0>>2), ie no change */
        if (phase & 0x200) {
            if (noise) {
                phase = 0x200 | 0xd0;
            }
        } else {
            /* when phase & 0x200 is clear and noise=1 then phase = 0xd0>>2 */
            /* when phase & 0x200 is clear and noise=0 then phase = 0xd0, ie no change */
            if (noise) {
                phase = 0xd0 >> 2;
            }
        }

        output[0] += op_calc(phase << FREQ_SH, env, 0, SLOT7_1->wavetable) * 2;
    }

    /* Snare Drum (verified on real YM3812) */
    env = volume_calc(SLOT7_2);
    if (env < ENV_QUIET) {
        /* base frequency derived from operator 1 in channel 7 */
        unsigned char bit8 = ((SLOT7_1->Cnt >> FREQ_SH) >> 8) & 1;

        /* when bit8 = 0 phase = 0x100; */
        /* when bit8 = 1 phase = 0x200; */
        UINT32 phase = bit8 ? 0x200 : 0x100;

        /* Noise bit XOR'es phase by 0x100 */
        /* when noisebit = 0 pass the phase from calculation above */
        /* when noisebit = 1 phase ^= 0x100; */
        /* in other words: phase ^= (noisebit<<8); */
        if (noise) {
            phase ^= 0x100;
        }

        output[0] += op_calc(phase << FREQ_SH, env, 0, SLOT7_2->wavetable) * 2;
    }

    /* Tom Tom (verified on real YM3812) */
    env = volume_calc(SLOT8_1);
    if (env < ENV_QUIET) {
        output[0] += op_calc(SLOT8_1->Cnt, env, 0, SLOT8_1->wavetable) * 2;
    }

    /* Top Cymbal (verified on real YM3812) */
    env = volume_calc(SLOT8_2);
    if (env < ENV_QUIET) {
        /* base frequency derived from operator 1 in channel 7 */
        unsigned char bit7 = ((SLOT7_1->Cnt >> FREQ_SH) >> 7) & 1;
        unsigned char bit3 = ((SLOT7_1->Cnt >> FREQ_SH) >> 3) & 1;
        unsigned char bit2 = ((SLOT7_1->Cnt >> FREQ_SH) >> 2) & 1;

        unsigned char res1 = (bit2 ^ bit7) | bit3;

        /* when res1 = 0 phase = 0x000 | 0x100; */
        /* when res1 = 1 phase = 0x200 | 0x100; */
        UINT32 phase = res1 ? 0x300 : 0x100;

        /* enable gate based on frequency of operator 2 in channel 8 */
        unsigned char bit5e = ((SLOT8_2->Cnt >> FREQ_SH) >> 5) & 1;
        unsigned char bit3e = ((SLOT8_2->Cnt >> FREQ_SH) >> 3) & 1;

        unsigned char res2 = (bit3e ^ bit5e);

        /* when res2 = 0 pass the phase from calculation above (res1); */
        /* when res2 = 1 phase = 0x200 | 0x100; */
        if (res2) {
            phase = 0x300;
        }

        output[0] += op_calc(phase << FREQ_SH, env, 0, SLOT8_2->wavetable) * 2;
    }
}

/* generic table initialize */
static int init_tables(void)
{
    signed int i, x;
    signed int n;
    double o, m;

    for (x = 0; x < TL_RES_LEN; x++) {
        m = (1 << 16) / pow(2, (x + 1) * (ENV_STEP / 4.0) / 8.0);
        m = floor(m);

        /* we never reach (1<<16) here due to the (x+1) */
        /* result fits within 16 bits at maximum */

        n = (int)m;             /* 16 bits here */
        n >>= 4;                /* 12 bits here */
        if (n & 1) {            /* round to nearest */
            n = (n >> 1) + 1;
        } else {
            n = n >> 1;
        }
        /* 11 bits here (rounded) */
        n <<= 1;                /* 12 bits here (as in real chip) */
        tl_tab[x * 2 + 0] = n;
        tl_tab[x * 2 + 1] = -tl_tab[x * 2 + 0];

        for (i = 1; i < 12; i++) {
            tl_tab[x * 2 + 0 + i * 2 * TL_RES_LEN] = tl_tab[x * 2 + 0] >> i;
            tl_tab[x * 2 + 1 + i * 2 * TL_RES_LEN] = -tl_tab[x * 2 + 0 + i * 2 * TL_RES_LEN];
        }
    }

    for (i = 0; i < SIN_LEN; i++) {
        /* non-standard sinus */
        m = sin(((i * 2) + 1) * M_PI / SIN_LEN ); /* checked against the real chip */

        /* we never reach zero here due to ((i * 2) + 1) */

        if (m > 0.0) {
            o = 8 * log(1.0 / m) / log(2.0);    /* convert to 'decibels' */
        } else {
            o = 8 * log(-1.0 / m) / log(2.0);   /* convert to 'decibels' */
        }

        o = o / (ENV_STEP / 4);

        n = (int)(2.0 * o);
        if (n & 1) {                                            /* round to nearest */
            n = (n >> 1) + 1;
        } else {
            n = n >> 1;
        }
        sin_tab[i] = n * 2 + (m >= 0.0 ? 0 : 1);
    }

    for (i = 0; i < SIN_LEN; i++) {
        /* waveform 1:  __      __     */
        /*             /  \____/  \____*/
        /* output only first half of the sinus waveform (positive one) */

        if (i & (1 << (SIN_BITS - 1))) {
            sin_tab[1 * SIN_LEN + i] = TL_TAB_LEN;
        } else {
            sin_tab[1 * SIN_LEN + i] = sin_tab[i];
        }

        /* waveform 2:  __  __  __  __ */
        /*             /  \/  \/  \/  \*/
        /* abs(sin) */

        sin_tab[2 * SIN_LEN + i] = sin_tab[i & (SIN_MASK >> 1)];

        /* waveform 3:  _   _   _   _  */
        /*             / |_/ |_/ |_/ |_*/
        /* abs(output only first quarter of the sinus waveform) */

        if (i & (1 << (SIN_BITS - 2))) {
            sin_tab[3 * SIN_LEN + i] = TL_TAB_LEN;
        } else {
            sin_tab[3 * SIN_LEN + i] = sin_tab[i & (SIN_MASK >> 2)];
        }
    }

    return 1;
}

static void OPLCloseTable( void )
{
}

static void OPL_initalize(FM_OPL *OPL)
{
    int i;

    /* frequency base */
    OPL->freqbase = (OPL->rate) ? ((double)OPL->clock / 72.0) / OPL->rate : 0;

    /* make fnumber -> increment counter table */
    for (i = 0; i < 1024; i++) {
        /* opn phase increment counter = 20bit */
        OPL->fn_tab[i] = (UINT32)((double)i * 64 * OPL->freqbase * (1 << (FREQ_SH - 10))); /* -10 because chip works with 10.10 fixed point, while we use 16.16 */
    }

    /* Amplitude modulation: 27 output levels (triangle waveform); 1 level takes one of: 192, 256 or 448 samples */
    /* One entry from LFO_AM_TABLE lasts for 64 samples */
    OPL->lfo_am_inc = (UINT32)((1.0 / 64.0) * (1 << LFO_SH) * OPL->freqbase);

    /* Vibrato: 8 output levels (triangle waveform); 1 level takes 1024 samples */
    OPL->lfo_pm_inc = (UINT32)((1.0 / 1024.0) * (1 << LFO_SH) * OPL->freqbase);

    /* Noise generator: a step takes 1 sample */
    OPL->noise_f = (UINT32)((1.0 / 1.0) * (1 << FREQ_SH) * OPL->freqbase);

    OPL->eg_timer_add = (UINT32)((1 << EG_SH) * OPL->freqbase);
    OPL->eg_timer_overflow = (1) * (1 << EG_SH);
}

inline static void FM_KEYON(OPL_SLOT *SLOT, UINT32 key_set)
{
    if (!SLOT->key) {
        /* restart Phase Generator */
        SLOT->Cnt = 0;

        /* phase -> Attack */
        SLOT->state = EG_ATT;
    }
    SLOT->key |= key_set;
}

inline static void FM_KEYOFF(OPL_SLOT *SLOT, UINT32 key_clr)
{
    if (SLOT->key) {
        SLOT->key &= key_clr;

        if (!SLOT->key) {
            /* phase -> Release */
            if (SLOT->state > EG_REL) {
                SLOT->state = EG_REL;
            }
        }
    }
}

/* update phase increment counter of operator (also update the EG rates if necessary) */
inline static void CALC_FCSLOT(OPL_CH *CH, OPL_SLOT *SLOT)
{
    int ksr;

    /* (frequency) phase increment counter */
    SLOT->Incr = CH->fc * SLOT->mul;
    ksr = CH->kcode >> SLOT->KSR;

    if (SLOT->ksr != ksr) {
        SLOT->ksr = ksr;

        /* calculate envelope generator rates */
        if ((SLOT->ar + SLOT->ksr) < 16 + 62) {
            SLOT->eg_sh_ar = eg_rate_shift[SLOT->ar + SLOT->ksr];
            SLOT->eg_sel_ar = eg_rate_select[SLOT->ar + SLOT->ksr];
        } else {
            SLOT->eg_sh_ar = 0;
            SLOT->eg_sel_ar = 13 * RATE_STEPS;
        }
        SLOT->eg_sh_dr = eg_rate_shift[SLOT->dr + SLOT->ksr];
        SLOT->eg_sel_dr = eg_rate_select[SLOT->dr + SLOT->ksr];
        SLOT->eg_sh_rr = eg_rate_shift [SLOT->rr + SLOT->ksr];
        SLOT->eg_sel_rr = eg_rate_select[SLOT->rr + SLOT->ksr];
    }
}

/* set multi,am,vib,EG-TYP,KSR,mul */
inline static void set_mul(FM_OPL *OPL, int slot, int v)
{
    OPL_CH *CH = &OPL->P_CH[slot / 2];
    OPL_SLOT *SLOT = &CH->SLOT[slot & 1];

    SLOT->mul = (UINT8)(mul_tab[v & 0x0f]);
    SLOT->KSR = (v & 0x10) ? 0 : 2;
    SLOT->eg_type = (v & 0x20);
    SLOT->vib = (v & 0x40);
    SLOT->AMmask = (v & 0x80) ? ~0 : 0;
    CALC_FCSLOT(CH, SLOT);
}

/* set ksl & tl */
inline static void set_ksl_tl(FM_OPL *OPL, int slot, int v)
{
    OPL_CH *CH = &OPL->P_CH[slot / 2];
    OPL_SLOT *SLOT = &CH->SLOT[slot & 1];
    int ksl = v >> 6; /* 0 / 1.5 / 3.0 / 6.0 dB/OCT */

    SLOT->ksl = ksl ? 3 - ksl : 31;
    SLOT->TL = (v & 0x3f) << (ENV_BITS - 1 - 7); /* 7 bits TL (bit 6 = always 0) */

    SLOT->TLL = SLOT->TL + (CH->ksl_base >> SLOT->ksl);
}

/* set attack rate & decay rate  */
inline static void set_ar_dr(FM_OPL *OPL, int slot, int v)
{
    OPL_CH *CH = &OPL->P_CH[slot / 2];
    OPL_SLOT *SLOT = &CH->SLOT[slot & 1];

    SLOT->ar = (v >> 4) ? 16 + ((v >> 4) << 2) : 0;

    if ((SLOT->ar + SLOT->ksr) < 16 + 62) {
        SLOT->eg_sh_ar = eg_rate_shift[SLOT->ar + SLOT->ksr];
        SLOT->eg_sel_ar = eg_rate_select[SLOT->ar + SLOT->ksr];
    } else {
        SLOT->eg_sh_ar = 0;
        SLOT->eg_sel_ar = 13 * RATE_STEPS;
    }

    SLOT->dr = (v & 0x0f) ? 16 + ((v & 0x0f) << 2) : 0;
    SLOT->eg_sh_dr = eg_rate_shift[SLOT->dr + SLOT->ksr];
    SLOT->eg_sel_dr = eg_rate_select[SLOT->dr + SLOT->ksr];
}

/* set sustain level & release rate */
inline static void set_sl_rr(FM_OPL *OPL, int slot, int v)
{
    OPL_CH *CH = &OPL->P_CH[slot / 2];
    OPL_SLOT *SLOT = &CH->SLOT[slot & 1];

    SLOT->sl = sl_tab[v >> 4];

    SLOT->rr = (v & 0x0f) ? 16 + ((v & 0x0f) << 2) : 0;
    SLOT->eg_sh_rr = eg_rate_shift[SLOT->rr + SLOT->ksr];
    SLOT->eg_sel_rr = eg_rate_select[SLOT->rr + SLOT->ksr];
}

/* write a value v to register r on OPL chip */
static void OPLWriteReg(FM_OPL *OPL, int r, int v)
{
    OPL_CH *CH;
    int slot;
    int block_fnum;

    /* adjust bus to 8 bits */
    r &= 0xff;
    v &= 0xff;

    switch (r & 0xe0) {
        case 0x00:      /* 00-1f:control */
            switch (r & 0x1f) {
                case 0x01:      /* waveform select enable */
                    if (OPL->type & OPL_TYPE_WAVESEL) {
                        OPL->wavesel = v & 0x20;
                        /* do not change the waveform previously selected */
                    }
                    break;
                case 0x02:      /* Timer 1 */
                    OPL->T[0] = (256 - v) * 4;
                    break;
                case 0x03:      /* Timer 2 */
                    OPL->T[1] = (256 - v) * 16;
                    break;
                case 0x04:      /* IRQ clear / mask and Timer enable */
                    if (v & 0x80) {     /* IRQ flag clear */
                        OPL_STATUS_RESET(OPL, 0x7f - 0x08); /* don't reset BFRDY flag or we will have to call deltat module to set the flag */
                    } else {    /* set IRQ mask ,timer enable*/
                        UINT8 st1 = v & 1;
                        UINT8 st2 = (v >> 1) & 1;

                        /* IRQRST,T1MSK,t2MSK,EOSMSK,BRMSK,x,ST2,ST1 */
                        OPL_STATUS_RESET(OPL, v & (0x78 - 0x08));
                        OPL_STATUSMASK_SET(OPL, (~v) & 0x78);

                        /* timer 2 */
                        if (OPL->st[1] != st2) {
                            OPL->st[1] = st2;
                        }

                        /* timer 1 */
                        if (OPL->st[0] != st1) {
                            OPL->st[0] = st1;
                        }
                    }
                    break;
                case 0x08:      /* MODE,DELTA-T control 2 : CSM,NOTESEL,x,x,smpl,da/ad,64k,rom */
                    OPL->mode = v;
                    break;
                default:
                    break;
            }
            break;
        case 0x20:      /* am ON, vib ON, ksr, eg_type, mul */
            slot = slot_array[r & 0x1f];
            if (slot < 0) {
                return;
            }
            set_mul(OPL, slot, v);
            break;
        case 0x40:
            slot = slot_array[r & 0x1f];
            if (slot < 0) {
                return;
            }
            set_ksl_tl(OPL, slot, v);
            break;
        case 0x60:
            slot = slot_array[r & 0x1f];
            if (slot < 0) {
                return;
            }
            set_ar_dr(OPL, slot, v);
            break;
        case 0x80:
            slot = slot_array[r & 0x1f];
            if (slot < 0) {
                return;
            }
            set_sl_rr(OPL, slot, v);
            break;
        case 0xa0:
            if (r == 0xbd) {                    /* am depth, vibrato depth, r,bd,sd,tom,tc,hh */
                OPL->lfo_am_depth = v & 0x80;
                OPL->lfo_pm_depth_range = (v & 0x40) ? 8 : 0;

                OPL->rhythm = v & 0x3f;

                if (OPL->rhythm & 0x20) {
                    /* BD key on/off */
                    if (v & 0x10) {
                        FM_KEYON(&OPL->P_CH[6].SLOT[SLOT1], 2);
                        FM_KEYON(&OPL->P_CH[6].SLOT[SLOT2], 2);
                    } else {
                        FM_KEYOFF(&OPL->P_CH[6].SLOT[SLOT1], ~2);
                        FM_KEYOFF(&OPL->P_CH[6].SLOT[SLOT2], ~2);
                    }
                    /* HH key on/off */
                    if (v & 0x01) {
                        FM_KEYON(&OPL->P_CH[7].SLOT[SLOT1], 2);
                    } else {
                        FM_KEYOFF(&OPL->P_CH[7].SLOT[SLOT1], ~2);
                    }

                    /* SD key on/off */
                    if (v & 0x08) {
                        FM_KEYON(&OPL->P_CH[7].SLOT[SLOT2], 2);
                    } else {
                        FM_KEYOFF(&OPL->P_CH[7].SLOT[SLOT2], ~2);
                    }

                    /* TOM key on/off */
                    if (v & 0x04) {
                        FM_KEYON(&OPL->P_CH[8].SLOT[SLOT1], 2);
                    } else {
                        FM_KEYOFF(&OPL->P_CH[8].SLOT[SLOT1], ~2);
                    }

                    /* TOP-CY key on/off */
                    if (v & 0x02) {
                        FM_KEYON(&OPL->P_CH[8].SLOT[SLOT2], 2);
                    } else {
                        FM_KEYOFF(&OPL->P_CH[8].SLOT[SLOT2], ~2);
                    }
                } else {
                    /* BD key off */
                    FM_KEYOFF(&OPL->P_CH[6].SLOT[SLOT1], ~2);
                    FM_KEYOFF(&OPL->P_CH[6].SLOT[SLOT2], ~2);

                    /* HH key off */
                    FM_KEYOFF(&OPL->P_CH[7].SLOT[SLOT1], ~2);

                    /* SD key off */
                    FM_KEYOFF(&OPL->P_CH[7].SLOT[SLOT2], ~2);

                    /* TOM key off */
                    FM_KEYOFF(&OPL->P_CH[8].SLOT[SLOT1], ~2);

                    /* TOP-CY off */
                    FM_KEYOFF(&OPL->P_CH[8].SLOT[SLOT2], ~2);
                }
                return;
            }
            /* keyon,block,fnum */
            if ((r & 0x0f) > 8) {
                return;
            }
            CH = &OPL->P_CH[r & 0x0f];
            if (!(r & 0x10)) {          /* a0-a8 */
                block_fnum = (CH->block_fnum & 0x1f00) | v;
            } else {    /* b0-b8 */
                block_fnum = ((v & 0x1f) << 8) | (CH->block_fnum & 0xff);

                if (v & 0x20) {
                    FM_KEYON(&CH->SLOT[SLOT1], 1);
                    FM_KEYON(&CH->SLOT[SLOT2], 1);
                } else {
                    FM_KEYOFF(&CH->SLOT[SLOT1], ~1);
                    FM_KEYOFF(&CH->SLOT[SLOT2], ~1);
                }
            }
            /* update */
            if (CH->block_fnum != (UINT32)block_fnum) {
                UINT8 block = block_fnum >> 10;

                CH->block_fnum = (UINT32)block_fnum;

                CH->ksl_base = (UINT32)(ksl_tab[block_fnum >> 6]);
                CH->fc = OPL->fn_tab[block_fnum & 0x03ff] >> (7 - block);

                /* BLK 2,1,0 bits -> bits 3,2,1 of kcode */
                CH->kcode = (CH->block_fnum & 0x1c00) >> 9;

                /* the info below is actually opposite to what is stated in the Manuals (verifed on real YM3812) */
                /* if notesel == 0 -> lsb of kcode is bit 10 (MSB) of fnum  */
                /* if notesel == 1 -> lsb of kcode is bit 9 (MSB-1) of fnum */
                if (OPL->mode & 0x40) {
                    CH->kcode |= (CH->block_fnum & 0x100) >> 8; /* notesel == 1 */
                } else {
                    CH->kcode |= (CH->block_fnum & 0x200) >> 9; /* notesel == 0 */
                }

                /* refresh Total Level in both SLOTs of this channel */
                CH->SLOT[SLOT1].TLL = CH->SLOT[SLOT1].TL + (CH->ksl_base >> CH->SLOT[SLOT1].ksl);
                CH->SLOT[SLOT2].TLL = CH->SLOT[SLOT2].TL + (CH->ksl_base >> CH->SLOT[SLOT2].ksl);

                /* refresh frequency counter in both SLOTs of this channel */
                CALC_FCSLOT(CH, &CH->SLOT[SLOT1]);
                CALC_FCSLOT(CH, &CH->SLOT[SLOT2]);
            }
            break;
        case 0xc0:
            /* FB,C */
            if ((r & 0x0f) > 8) {
                return;
            }
            CH = &OPL->P_CH[r & 0x0f];
            CH->SLOT[SLOT1].FB = (v >> 1) & 7 ? ((v >> 1) & 7) + 7 : 0;
            CH->SLOT[SLOT1].CON = v & 1;
            CH->SLOT[SLOT1].connect1 = CH->SLOT[SLOT1].CON ? &output[0] : &phase_modulation;
            break;
        case 0xe0: /* waveform select */
            /* simply ignore write to the waveform select register if selecting not enabled in test register */
            if (OPL->wavesel) {
                slot = slot_array[r & 0x1f];
                if (slot < 0) {
                    return;
                }
                CH = &OPL->P_CH[slot / 2];

                CH->SLOT[slot & 1].wavetable = (UINT16)((v & 0x03) * SIN_LEN);
            }
            break;
    }
}

/* lock/unlock for common table */
static int OPL_LockTable(void)
{
    num_lock++;
    if (num_lock > 1) {
        return 0;
    }

    /* first time */

    cur_chip = NULL;
    /* allocate total level table (128kb space) */
    if (!init_tables()) {
        num_lock--;
        return -1;
    }

    return 0;
}

static void OPL_UnLockTable(void)
{
    if (num_lock) {
        num_lock--;
    }
    if (num_lock) {
        return;
    }

    /* last time */

    cur_chip = NULL;
    OPLCloseTable();
}

static void OPLResetChip(FM_OPL *OPL)
{
    int c, s;
    int i;

    OPL->eg_timer = 0;
    OPL->eg_cnt = 0;

    OPL->noise_rng = 1; /* noise shift register */
    OPL->mode = 0;      /* normal mode */
    OPL_STATUS_RESET(OPL, 0x7f);

    /* reset with register write */
    OPLWriteReg(OPL, 0x01, 0); /* wavesel disable */
    OPLWriteReg(OPL, 0x02, 0); /* Timer1 */
    OPLWriteReg(OPL, 0x03, 0); /* Timer2 */
    OPLWriteReg(OPL, 0x04, 0); /* IRQ mask clear */
    for (i = 0xff; i >= 0x20; i--) {
        OPLWriteReg(OPL, i, 0);
    }

    /* reset operator parameters */
    for (c = 0; c < 9; c++) {
        OPL_CH *CH = &OPL->P_CH[c];
        for (s = 0; s < 2; s++) {
            /* wave table */
            CH->SLOT[s].wavetable = 0;
            CH->SLOT[s].state = EG_OFF;
            CH->SLOT[s].volume = MAX_ATT_INDEX;
            CH->SLOT[s].connect1 = &output[0];
        }
    }
}

/* Create one of virtual YM3812/YM3526 */
/* 'clock' is chip clock in Hz  */
/* 'rate'  is sampling rate  */
static FM_OPL *OPLCreate(UINT32 clock, UINT32 rate, int type)
{
    char *ptr;
    FM_OPL *OPL;
    int state_size;

    if (OPL_LockTable() == -1) {
        return NULL;
    }

    /* calculate OPL state size */
    state_size = sizeof(FM_OPL);

    /* allocate memory block */
    ptr = lib_malloc(state_size);

    if (ptr == NULL) {
        return NULL;
    }

    /* clear */
    memset(ptr, 0, state_size);

    OPL = (FM_OPL *)ptr;

    ptr += sizeof(FM_OPL);

    OPL->type = type;
    OPL->clock = clock;
    OPL->rate = rate;

    /* init global tables */
    OPL_initalize(OPL);

    return OPL;
}

/* Destroy one of virtual YM3812 */
static void OPLDestroy(FM_OPL *OPL)
{
    OPL_UnLockTable();
    lib_free(OPL);
}

static int OPLWrite(FM_OPL *OPL, int a, int v)
{
    if (!(a & 1)) {       /* address port */
        OPL->address = v & 0xff;
    } else {    /* data port */
        OPLWriteReg(OPL, OPL->address, v);
    }
    return OPL->status >> 7;
}

static unsigned char OPLRead(FM_OPL *OPL, int a)
{
    if (!(a & 1)) {
        /* OPL and OPL2 */
        return OPL->status & (OPL->statusmask | 0x80);
    }

    return 0xff;
}

/* CSM Key Controll */
inline static void CSMKeyControll(OPL_CH *CH)
{
    FM_KEYON(&CH->SLOT[SLOT1], 4);
    FM_KEYON(&CH->SLOT[SLOT2], 4);

    /* The key off should happen exactly one sample later - not implemented correctly yet */
    FM_KEYOFF(&CH->SLOT[SLOT1], ~4);
    FM_KEYOFF(&CH->SLOT[SLOT2], ~4);
}

static int OPLTimerOver(FM_OPL *OPL, int c)
{
    if (c) {    /* Timer B */
        OPL_STATUS_SET(OPL, 0x20);
    } else {    /* Timer A */
        OPL_STATUS_SET(OPL, 0x40);
        /* CSM mode key,TL controll */
        if (OPL->mode & 0x80) { /* CSM mode total level latch and auto key on */
            int ch;

            for (ch = 0; ch < 9; ch++) {
                CSMKeyControll(&OPL->P_CH[ch]);
            }
        }
    }
    /* reload timer */
    return OPL->status >> 7;
}

#define MAX_OPL_CHIPS 2

FM_OPL *ym3812_init(UINT32 clock, UINT32 rate)
{
    /* emulator create */
    FM_OPL *YM3812 = OPLCreate(clock, rate, OPL_TYPE_YM3812);
    if (YM3812) {
        ym3812_reset_chip(YM3812);
    }
    return YM3812;
}

int connect1_is_output0(int *connect)
{
    if (connect == &output[0]) {
        return 1;
    }
    return 0;
}

void set_connect1(int *connect, int output0)
{
    if (output0) {
        connect = &output[0];
    } else {
        connect = &phase_modulation;
    }
}

void ym3812_shutdown(FM_OPL *chip)
{
    OPLDestroy(chip);
}

void ym3812_reset_chip(FM_OPL *chip)
{
    OPLResetChip(chip);
}

int ym3812_write(FM_OPL *chip, int a, int v)
{
    return OPLWrite(chip, a, v);
}

unsigned char ym3812_read(FM_OPL *chip, int a)
{
    /* YM3812 always returns bit2 and bit1 in HIGH state */
    return OPLRead(chip, a) | 0x06;
}

unsigned char ym3812_peek(FM_OPL *chip, int a)
{
    /* YM3812 always returns bit2 and bit1 in HIGH state */
    return OPLRead(chip, a) | 0x06;
}

int ym3812_timer_over(FM_OPL *chip, int c)
{
    return OPLTimerOver(chip, c);
}

/*
** Generate samples for one of the YM3812's
**
** 'which' is the virtual YM3812 number
** '*buffer' is the output buffer pointer
** 'length' is the number of samples that should be generated
*/
void ym3812_update_one(FM_OPL *chip, OPLSAMPLE *buffer, int length)
{
    FM_OPL *OPL = (FM_OPL *)chip;
    UINT8 rhythm = OPL->rhythm & 0x20;
    OPLSAMPLE *buf = buffer;
    int i;

    if ((void *)OPL != cur_chip) {
        cur_chip = (void *)OPL;
        /* rhythm slots */
        SLOT7_1 = &OPL->P_CH[7].SLOT[SLOT1];
        SLOT7_2 = &OPL->P_CH[7].SLOT[SLOT2];
        SLOT8_1 = &OPL->P_CH[8].SLOT[SLOT1];
        SLOT8_2 = &OPL->P_CH[8].SLOT[SLOT2];
    }
    for (i = 0; i < length; i++) {
        int lt;

        output[0] = 0;

        advance_lfo(OPL);

        /* FM part */
        OPL_CALC_CH(&OPL->P_CH[0]);
        OPL_CALC_CH(&OPL->P_CH[1]);
        OPL_CALC_CH(&OPL->P_CH[2]);
        OPL_CALC_CH(&OPL->P_CH[3]);
        OPL_CALC_CH(&OPL->P_CH[4]);
        OPL_CALC_CH(&OPL->P_CH[5]);

        if (!rhythm) {
            OPL_CALC_CH(&OPL->P_CH[6]);
            OPL_CALC_CH(&OPL->P_CH[7]);
            OPL_CALC_CH(&OPL->P_CH[8]);
        } else {                /* Rhythm part */
            OPL_CALC_RH(&OPL->P_CH[0], (OPL->noise_rng >> 0) & 1 );
        }

        lt = output[0];

        lt >>= FINAL_SH;

        /* limit check */
        lt = limit(lt, MAXOUT, MINOUT);

        /* store to sound buffer */
        buf[i] = lt;

        advance(OPL);
    }
}

FM_OPL *ym3526_init(UINT32 clock, UINT32 rate)
{
    /* emulator create */
    FM_OPL *YM3526 = OPLCreate(clock, rate, OPL_TYPE_YM3526);
    if (YM3526) {
        ym3526_reset_chip(YM3526);
    }
    return YM3526;
}

void ym3526_shutdown(FM_OPL *chip)
{
    OPLDestroy(chip);
}

void ym3526_reset_chip(FM_OPL *chip)
{
    OPLResetChip(chip);
}

int ym3526_write(FM_OPL *chip, int a, int v)
{
    return OPLWrite(chip, a, v);
}

unsigned char ym3526_read(FM_OPL *chip, int a)
{
    /* YM3526 always returns bit2 and bit1 in HIGH state */
    return OPLRead(chip, a) | 0x06;
}

unsigned char ym3526_peek(FM_OPL *chip, int a)
{
    /* YM3526 always returns bit2 and bit1 in HIGH state */
    return OPLRead(chip, a) | 0x06;
}

int ym3526_timer_over(FM_OPL *chip, int c)
{
    return OPLTimerOver(chip, c);
}

/*
** Generate samples for one of the YM3526's
**
** 'which' is the virtual YM3526 number
** '*buffer' is the output buffer pointer
** 'length' is the number of samples that should be generated
*/
void ym3526_update_one(FM_OPL *chip, OPLSAMPLE *buffer, int length)
{
    FM_OPL *OPL = (FM_OPL *)chip;
    UINT8 rhythm = OPL->rhythm & 0x20;
    OPLSAMPLE *buf = buffer;
    int i;

    if ((void *)OPL != cur_chip) {
        cur_chip = (void *)OPL;
        /* rhythm slots */
        SLOT7_1 = &OPL->P_CH[7].SLOT[SLOT1];
        SLOT7_2 = &OPL->P_CH[7].SLOT[SLOT2];
        SLOT8_1 = &OPL->P_CH[8].SLOT[SLOT1];
        SLOT8_2 = &OPL->P_CH[8].SLOT[SLOT2];
    }
    for (i = 0; i < length; i++) {
        int lt;

        output[0] = 0;

        advance_lfo(OPL);

        /* FM part */
        OPL_CALC_CH(&OPL->P_CH[0]);
        OPL_CALC_CH(&OPL->P_CH[1]);
        OPL_CALC_CH(&OPL->P_CH[2]);
        OPL_CALC_CH(&OPL->P_CH[3]);
        OPL_CALC_CH(&OPL->P_CH[4]);
        OPL_CALC_CH(&OPL->P_CH[5]);

        if (!rhythm) {
            OPL_CALC_CH(&OPL->P_CH[6]);
            OPL_CALC_CH(&OPL->P_CH[7]);
            OPL_CALC_CH(&OPL->P_CH[8]);
        } else {                /* Rhythm part */
            OPL_CALC_RH(&OPL->P_CH[0], (OPL->noise_rng >> 0) & 1);
        }

        lt = output[0];

        lt >>= FINAL_SH;

        /* limit check */
        lt = limit(lt, MAXOUT, MINOUT);

        /* store to sound buffer */
        buf[i] = lt;

        advance(OPL);
    }
}

/* ---------------------------------------------------------------------*/
/*    snapshot support functions                                             */

#define CART_DUMP_VER_MAJOR   0
#define CART_DUMP_VER_MINOR   0
#define SNAP_MODULE_NAME  "YM3526"

/* FIXME: implement snapshot support */
int ym3526_snapshot_write_module(snapshot_t *s)
{
    return -1;
#if 0
    snapshot_module_t *m;

    m = snapshot_module_create(s, SNAP_MODULE_NAME,
                               CART_DUMP_VER_MAJOR, CART_DUMP_VER_MINOR);
    if (m == NULL) {
        return -1;
    }

    if (0) {
        snapshot_module_close(m);
        return -1;
    }

    snapshot_module_close(m);
    return 0;
#endif
}

int ym3526_snapshot_read_module(snapshot_t *s)
{
    return -1;
#if 0
    BYTE vmajor, vminor;
    snapshot_module_t *m;

    m = snapshot_module_open(s, SNAP_MODULE_NAME, &vmajor, &vminor);
    if (m == NULL) {
        return -1;
    }

    if ((vmajor != CART_DUMP_VER_MAJOR) || (vminor != CART_DUMP_VER_MINOR)) {
        snapshot_module_close(m);
        return -1;
    }

    if (0) {
        snapshot_module_close(m);
        return -1;
    }

    snapshot_module_close(m);
    return 0;
#endif
}
